In order to increase yield and improve quality of crops such as fruits and vegetables, various growth promoting agents, plant growth adjustment agents, physiological activity promoting agents, taste improvement agents, and the like that are sprayed onto leaf surfaces of fruits and vegetables or onto soil have been suggested. In recent years, focus has also fallen on vegetables having standardized functional ingredients such as lycopene and potassium.
Known examples include a foliar surface spray for grapes that contains calcium formate and a boron compound (Patent Literature 1), and a growth promoting agent and physiological activity promoting agent that are sprayed on soil or a leaf surface and have a nucleic acid-based component such as nucleotides as an active ingredient (Patent Literatures 2 and 3). For supplying a nitrogen component via a leaf surface, Patent Literature 4 describes using not only urea nitrogen but also an amino acid nitrogen, and employing a substance in which protein from albumen or powdered fat-free milk has been fermented with yeast. In addition, a cell wall decomposition product derived from brewer's yeast is known to improve the taste of an edible portion of a plant (Patent Literature 5). A composition for plants has been sought that broadly brings together these effects of promoting growth and improving quality of crops, has an elevated effect, and that is safer and easy to handle.